We propose three related projects all focused on control of the major vector, Aedes aegypti, of dengue fever in Brazil. We have developed a powerful new tool for genetic analysis of this species of mosquito, a SNP chip with ~30,000 well-validated SNPs, that will applied in all three projects. The first project is an analysis of a release program using transgenic mosquitoes to suppress population numbers, the so-called RIDL technique. One unanswered question for any such program of this sort is whether the release of such mosquitoes has a lasting impact on the genetic make-up of the natural target population. We have genotyped (using our SNP chip) samples from one site before releases began as well as a sample of the release strain. We will sample the field site 6 months and 12 months after release to examine whether genetic material from the release strain is being transferred to the target population. If so, this has enormous implications for any such future releases of this sort. The second project focuses on studying the genetic underpinning of variation in the ability of female Ae. aegypti to transmit the dengue fever virus, DENV. Our SNP chip coupled with very recent significant advances in genome assembly make this an especially propitious time to undertake such studies. One issue never before addressed in such work is the degree to which populations of mosquito vary geographically in the genes or gene regions responsible for DENV competence. We will also address issues of temporal genetic stability for DENV competence. The third project is on evolution of insecticide resistance in Ae. aegypti in Brazil. Ongoing studies by colleagues at Fiocruz in Rio de Janeiro have revealed very interesting patterns of allele frequencies at the kdr locus responsible for resistance to pyrethroi insecticides. This includes worldwide patterns as well as detailed patterns in Brazil. We propose to continue these studies adding the important adjunct of 30K SNP data from the same samples as studied for kdr alleles. This will provide unprecedented information on evolution of resistance as well as address issues such as the origin of Ae. aegypti populations in Brazil and the timing and origin of insecticide resistance.